Dumbest Qn Ever- Extending Box Mix

I have never baked a cake that wasn't from "scratch" and before that starts a huge debate, it isn't because i dont want to or don't believe in it!The reason is, I don't know how! LOL

So, when i see the recipe for WASC cakes, and it says take a box mix and extend, I'm soooo excited to try but i have one stupid question stopping me...how?

do you "make" the box mix and then other ingredients, (so whatever ingredients are listed on the back of the box are ALSO required) or i s it quite literally only using the "mix" and you put it all together with other dry ingredients etc??

"A question for those that have tried the WASC cake recipe, is it a moist cake. Thanks so much"

It is if you add 1/2 cup mayo to this recipe above! I think it's moist even if you don't. I just have the habit of the Mayo now because it works EVERY time. Customers are always asking how I get my cakes so moist.

I use the WASC version that adds 1 cup of flour, 1 cup of sugar, 1 cup of sour cream, 1 cup of water, 1 tablespoon of extract, 3 eggs, and one box cake mix, and I've gotten rave reviews. It's moist and even a little sticky when leveling and moving around. I've used it for chocolate, white, white chocolate, caramel, orange, vanilla, spice, cherry, and I'm not sure what else. The only thing I've changed for any of them is the spice cake. I added a box of Pumpkin Spice instant pudding mix and an extra egg.